The fired equipment of the oil field is preferrably unattended except for its initial startup and periodic inspection. Therefore, automatic safety systems for both the pilot and main burners are required to avoid the main burner discharging raw fuel which will accumulate in explosive quantities within the fired equipment.
It has been the custom to mount a closed fluid pressure system so it is responsive to the pilot burner and will utilize the mechanical movement produced to maintain the connection of both burners to the fuel supply. Failure of heat at both the main burner and pilot burner reverses the mechanical movement of the system to disconnect the burners from their fuel supply. A cam, or ratchet, has been employed with which to manually connect the pilot burner to the fuel supply until the heat of the burner generates the mechanical movement with which to sustain the connection of the fuel supply to the pilot burner and simultaneously remove the temporary support to the connection afforded by the manually set cam, or ratchet. However, the present systems are arranged so that if the manually operated ratchet system is actuated and the pilot burner fails to remain ignited long enough to bring the closed fluid pressure system into operation long enough to release the ratchet, the main burner remains connected to the fuel supply and permits discharge of the raw fuel from the main burner to accumulate in explosive amounts within the fired equipment. Therefore, it is desirable to positively isolate the main burner from the fuel supply until the pilot burner has been "proved" which will include release of the ratchet mechanism by which the pilot burner was originally connected to the fuel supply.